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BQ24085 Datasheet, PDF (21/34 Pages) Texas Instruments – 750 mA SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION
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bq24085, bq24086
bq24087, bq24088
www.ti.com .................................................................................................................................................... SLUS784B – DECEMBER 2007 – REVISED MAY 2008
CHARGE TERMINATION DETECTION AND RECHARGE
The charging current is monitored the during the voltage regulation phase. Charge termination is indicated at the
STATx pins (STAT1 = Hi-Z; STAT2 = Low ) once the charge current falls below the termination current threshold
I(TERM). A deglitch period tDGL(TERM) is added to avoid false termination indication during transient events.
Charge termination is not detected if the charge current falls below the termination threshold as a result of the
thermal loop activation. Termination is also not detected when charger enters the suspend mode, due to
detection of invalid pack temperature or internal thermal shutdown.
Table 6 describes the termination latch functionality.
Table 6. Termination Latch Functionality
TERMINATION DETECTED LATCHED WHEN
I(OUT) < I(TERM) AND t > tDGL(TERM) AND V(OUT) > V(RCH)
TERMINATION LATCH RESET AT
CE rising edge or OVP detected
New charging cycle started; see state diagram
Termination disabled
The termination function is DISABLED:
1. In bq24085/6/7/8 the termination is disabled when the TMR pin is left open (floating).
2. In bq24087, leaving the TMR pin open (floating) does not disable the termination. The only way to disabled
termination in bq24087 is to have TE = high.
BATTERY ABSENT DETECTION – VOLTAGE MODE ALGORITHM
The bq24085/6/7/8 provides a battery absent detection scheme to reliably detect insertion and/or removal of
battery packs. The detection circuit applies an internal current to the battery terminal, and detects battery
presence based on the terminal voltage behavior. Figure 19 has a typical waveform of the output voltage when
the battery absent detection is enabled and no battery is connected:
5
4.50
4
3.50
3
2.50
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
t - Time - s
Figure 19. Battery-Absent Detection Waveforms
The battery absent detection function is disabled if the voltage at the BAT pin is held above the battery recharge
threshold, V(RCH), after termination detection. When the voltage at the BAT pin falls to the recharge threshold,
Copyright © 2007–2008, Texas Instruments Incorporated
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Product Folder Link(s): bq24085, bq24086 bq24087, bq24088
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